This invention relates generally to radiological apparatus and more particularly to means for simultaneously moving elements of an X-ray system in proper synchronism to achieve tomograms without any mechanical linkage between the source and image receptor.
Earlier systems for performing tomographic procedures which included linear, circular, trispiral and other complex motions, for example, required massive and complex precision mechanical linkages between the X-ray beam source and the X-ray receptor which may comprise a film holder or bucky, so that their respective motions can be precisely controlled with regard to the patient or object under examination.
More recently, U.S. Pat. No. 4,087,694, which issued on May 2, 1978, and entitled "Tomography System", by M. J. Hellstrom, et al. and in the above cross-referenced related application, U.S. Ser. No. 835,738, entitled "A System For Circular And Complex Tomography", M. J. Hellstrom, there is described linear and complex tomographic systems which included means for eliminating the conventional mechanical linkage between the overhead tube suspension or bridge and a bucky in an X-ray table. In both instances, measures of components of the position of the X-ray source are determined by means of radiant energy utilizing a laser interferometer. Changes in the position of the X-ray source are electronically scaled to determine the changes which must be made simultaneously to the position of the image receptor, meaning that the X-ray source is first driven and the changes in its position are measured, whereupon the image receptor is moved in a manner related to the measured changes of the position of the X-ray source. Movement in both cases is accomplished by stepper motors and an electronic system for generating pulse sequences for each of the stepper motors. Stepper motor translation of the image receptor is also disclosed in assignee's U.S. Pat. No. 4,095,110 entitled "Means For Stepping X-Ray Receptor In Direction Opposite To Position Change Of Source", which issued on June 13, 1978 in the name of L. R. Bunch.
In addition to the aforementioned systems, one other means is known for performing a tomographic procedure which obviates the need for mechanical linkage between the X-ray source and the receptor. Such apparatus is disclosed in U.S. Pat. No. 3,809,886, entitled "Dynamic Tomography With Movable Table", G. D. Cochran, et al. which issued on May 7, 1974.